Relief valve for rotary compressor



March 20, 1956 J. w. JACOBS RELIEF VALVE FOR ROTARY COMPRESSOR Filed Jan. '7, 1953 INVENTOR. James W. Jacobs Attorneys I H L z,7ss,6s7

RELIEF VALVE For: ROTARY COMPRESSOR Jame Jacobs; Dayton,- Ohio", assignor to General 1 De aware a Application January 7, 1953, Serial No. 330 ,040

" f .fz Claims, cl. sea-117.75 I

rs,C0rporation, Detroit; Mich a corporation of *This invention r elat es to refrigerating apparatus and more particularly to motor-compressor units used in re- 'frigerating systems. V a 7 Motor-compressor units of refrigerating systems sealed within a casing should be operated at a temperature that will not cause deterioration and damage to materials employed to cover and insulate electric wire windings of the" motor. The best motor winding cover materials known to date have been found to withstand temperatures up toapproximately 200 F. without becoming deteriorated orldamaged by refrigerant and oilsealed in a closed friefrigeratin'g system. If the temperature within a sealed linotor compressor unit of a refrigerating system increases far above 200 F. the refrigerant and oil deteriorates insulating material employed to cover the motor windings and causes this material to soften and become loose whereu on'it. will separate from the wires and create ishort circuitsin the motor. In order to keep the operating temperature of a motor-compressor unit as low as possible, refrigerant compressed thereby has been directed. out ofrthe sealed casing thereof through a super- ..heat removing coil or conduit, for removing heat of compression from the refrigerant, prior to flowing the same ;ba;ck.,into;the casing. This precooling of the fluid is ;quite common to those skilled in the artand is employed 'tocause a certain amount of oil to be separated from the compressed fluid and to be released therefrom upon 'reentering the sealed unit whereupon it flows to the bottomof the sealed casing of the unit and accumulates or isistoredtherein and utilized to lubricate operating parts of the compressor. It is also common in the art to provvide' an oil relief valve for the compression chamber of a sealed rotary motor-compressor unit so that globules of lubricant and/or slugs of liquid refrigerant drawn into the chamber will not damage the compressed refrigerant discharge valve of; the compressor or brake parts of the :unit. Such a relief valve has heretofore been designed to discharge the partially compressed globules of oil or 'sli1gs of liquid refrigerant from the compressor cylinder enemy into the sealed casing containing the motor and eera r ss'or. I have found that this discharge of oil or "liquid' refrigerant into the sealed casing, without being first ted; through "the 'superheat removing conduit icoil;, raise;s tl1 etemperature within thecasing ofa motor- {co Peaerpaaa a dangerous degree, such forexample,

' 'etween .230? and 260 l contemplate the pro- 'ofmea'ns .within a sealed motor-compressor unit ch willljprevent temporary or extended periods of eased or abnormally high temperatures therein to ebyeliminate'deterioration of and damage to the un ting material about wire windings of the electric rfmotor bje'ct of my invention is to improve and: prolong the life of asealed motor-compressor unit of a refrigerating system. a 1

*Another object of my inventionis to provide means whereby the temperature within a sealed casing housing "hism is mounted. The compressor a motor and compressor of a refrigerating system will remain substantially constant under various operating conditions of the compressor.

Still another object of my invention is to provide means in a sealed motor-compressor unit for flowing all fluid passing through the compressor out of the casing enclosing the unitintoa superheat removing conduit coil connected thereto so as to partially cool the same and remove heat of compression from the fluid prior to discharging it back into the unit.

, Afurther object of my invention is to insurethe discharge of globules of oil or slugs of liquid-refrigerant which might enter the compression chamber of a sealed motor-compressor unit, of the rotary type in a refrigerating system, out of the casing housing the unit to prevent the same from unduly increasing the temperature within the unit. i

A still further and more specific object of my invention is to provide means in a sealed motor-compressor unit of a refrigerating system for expelling slugs of oil and liquid refrigerant or globules of a mixture thereof from the compressor through a pressure relief valve out of the sealed unit by by-passing the same around the compressed refrigerant discharge valve into another element in the system.

Further objects. and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein 30 fa preferred form of the present invention is clearly shown.

In the drawings:

Figure/1 is a diagrammatic view of a closed refrigeratthereing Figure 2 is an enlarged fragmentary sectional view of the sealed motor-compressor unit employed in the system shown in Figure 1; and

Figure 3 is a horizontal sectional view of the compressor portion of the unit shown in Figure 2 and is taken on the line 3-3 thereof.

Referring now to Figure l of the drawings, the closed refrigerating system illustrated therein comprises an evaporator 11, preferably of the sheet metal type, a condenser 12, a motor-compressor unit sealed within a casing,

ing system having a superheat removing conduit coil generally represented by the reference numeral 15, and a superheat removing conduit coil 14 outside casing 15. Suitable refrigerant fiow conduit connections between the various elements of the refrigerating system are provided to form a closed circuit therebetween as will be hereinafter described. The electric motor of the sealed unit in casing 15 comprises a stator 16 having wire windings 17 associated therewith and a rotor 18, secured to a shaft 19, for driving the compressor of the unit (see Figure 2). This electric motor may be energized and deenergized by a suitable .or conventional thermostatic switch (not shown) responsiveto temperatures of evaporator 11 for starting and stopping the same. he sealed casing 15 includes an upper metal cover plate (not shown) welded orotherwise suitably secured to a lower metal cup-shaped member 21 within which the motor-compressor mechais generally represented by the reference numeral 22 and is mounted on a plurality of blocks 23, welded to the bottom wall of cup member 21, by a plurality of bolts 24. Compressor 22 is of the rotary type and includes a cylinderelement 26 forming a compression chamber 27 therein. Cylinder element 26 is disposed or sandwiched between upper and lower bearing end plates 28 and 29 respectively which close thetop and bottom of chamber 27. An impeller 31 .is located within the compression chamber 27 and is I 2,738,657 Patented Mar. 20, 1956' in one wall of the cylinder. element as best shown in Figure 3. Block 33 is biased into engagement with the impeller 31 by means of a spring 34 which is held in place within a suitable cavity provided in the cylinder element 26. The bottom bearing or end plate 29 is provided with arcfrigerant inlet hole 36 and an outlet hole 37 arranged as shown in Figure 3. A check valve (not shown) is provided for inlet hole 36 as is customary in the art. A spring pressed valve 38 (see Figure 2) covers the outlet hole 37 through which gaseous refrigerant compressed in chamber 27 is discharged. A large block 41, welded or otherwise suitably secured or sealed to the bottom Wall of cup member 21, is provided with a port (not shown) extending from the exterior thereof and communicating with the inlet hole 36. Block 41 is also provided with a port or passageway 42 extending from the exterior thereof and communicating with the valve 38 and outlet hole 37. A labyrinth-like passage muffier 43, of any suitable or conventional design and construction, is located in port 42 beyond the discharge valve 38.

Operation of the motor to drive the compressor 22 causes refrigerant and oil entrained therewith to be compressed by the impeller 31 in compression chamber 27 of cylinder element 26 and discharged out of the sealed casing 15. Operation of the compressor creates a suction within evaporator 11 or causes refrigerant therein to absorb heat and vaporize as is well known to those skilled in the art. The vaporized refrigerant is drawn through a conduit 46 (see Figure 1), extending from the block 41 to the evaporator 11, directly into the compression chamber 27 by way of inlet hole 36. Refrigerant compressed within compressor 22 is discharged directly out of the sealed casing 15 through outlet hole 37, past valve 38, into passageway 42 and through muffier 43 to a conduit 47, secured and sealed to passageway 42, leading to the finned superheat removing conduit coil 14. This coil 14 is exposed to ambient temperature outside the sealed motor-compressor unit and may have air forcibly circulated thereover. It is the purpose of coil 14 to remove some or all of the heat of compression from the compressed refrigerant gas so as to prevent this heat from being dissipated into the interior of the sealed motor-compressor unit to permit operation thereof at as low a temperature as is possible. Superheat removing coil 14 has its other end connected to the upper part of casing 15, by a conduit 49, so as to communicate with the interior thereof. The space within casing 15 about the motor-compressor unit therein forms a lubricant or oil separating and accumulating or storage chamber. Cooling of the compressed refrigerant in coil 14 causes lubricant entrained by the refrigerant gas to separate therefrom within the motor-compressor compartment of the sealed unit. The lubricant thus separated out of the refrigerant drains down into the lower portion of cup member 21 and accumulates in a body therein so as to supply lubricant to the operating parts of the compressor as needed. The separated lubricant is free to flow downwardly between the motor stator 16 and casing 21 or between the motor rotor 18 and its stator in the conventional manner. Compressor shaft 19 is provided with the usual form of oil feeding grooves to supply lubricant to bearing surfaces of the shaft. The substantially lubricant-free compressed refrigerant leaves the sealed unit through an outlet conduit 52 which leads to the main condenser 12 (see Figure l). Refrigerant which is cooled and condensed to liquid form in condenser 12 is supplied to the evaporator 11 by way of conduit 53, under the control of a suitable or conventional expansion valve or restrictor 54, in accordance with well known practice. The refrigerant vaporizing in evaporator 11 is again returned to the compressor through conduit 46.

Since small slugs of oil or liquid refrigerant or globules or both admixed together sometimes flow from the evaporator 11 directly into the compression chamber 27 of compressor 22, means must be provided to expel such liquid from the compression chamber to not only relieve the impeller 31 but to also prevent damaging the compressed refrigerant discharge valve. A spring pressed relief valve is usually provided for this purpose. Others have provided such a relief valve but have arranged the same in such a manner that the outlet port of the valve communicated with the interior of a sealed casing of a motor-compressor unit. In this type arrangement the slugs or globules of liquid are discharged directly;into the sealed casing. The partial compression of this liquid by the compressor impeller creates a high temperature of the liquid, which temperature is transmitted and dissrpated to the interior of the sealed motor-compressor unit and abnormally increases its internal. temperature thus establishing the problem hereinbefore described.

In the present invention a pressure relief valve 56 is seated upon a seat adjacent a shoulder formed at a reduced portion in a port opening 57 provided in the compressor upper bearing end plate 28. Opening 57 is above and in vertical alignment with the hole 37 in bottom end bearing plate 29. Valve 56 is biased upon its seat in port opening 57 by a coil spring 58. The upper end of port opening 57 is closed or sealed off from communicating with the lubricant separating and collecting chamber within casing 15 by a suitable plastic or the like plate 59 extending thereacross. A metal plate 61 is disposed over plate 59 and a washer 62 is placed under the head of a pair of screws 63 which are threaded into the compressor upper end plate 58. Plate 59, in addition to scaling the top of port opening 57 also forms a backing for spring 58. A passage 66 drilled, bored or otherwise suitably provided in compressor upper end plate 28 communicates at one end thereof with the port opening 57 and at its other end with a passage 67 provided through the cylinder element 26. Passage 68 provided in compressor lower end plate 29 has its one end communicating with passage 67 and has its other end registering with a passage 69 provided in the large block 41. The lower end of passage 69 opens .into and communicates with the passageway 42, leading to conduit 47, beyond or below the mufiier 43. The fluid flow passageway formed by the bores or passages 66, 67, 68 and 69 provides a by-pass, within compressor 22 located in the sealed casing 15, from port opening 57 around the compressed refrigerant discharge valve 38 and muffler 43 to the outlet port 42 and consequently conduit 47. Thus in the present structure any globules or slugs of liquid entering the compression chamber 27 of compressor 22 and partially compressed by the impeller 31 are discharged through the spring pressed valve 56 into port opening 57 and by way of the bores or passages 66, 67, 68, 69, port 42 and conduit 47 into the superheat removing conduit coil 14. Heat generated by the partial compression of the slugs or globules of liquid is carried therewith to coil 14 where this heat is given up to air outside sealed casing 15. In this manner all fluid entering the compressor 22, including globules of oil or slugs of liquid refrigerant as well as gaseous refrigerant to be compressed, is directed out of casing 15 and is precooled prior to reentering the same to prevent the heat of compression thereof from abnormally increasing the temperature within the sealed motor-compressor unit.

It should be apparent from the foregoing that I have provided means whereby a sealed motor-compressor unit of a closed refrigerating system may operate at substantially a constant temperature under varying operating conditions or characteristics within this system. My invention, in addition to preventing abnormal increases in temperature within the sealed casing of an enclosed motorcompressor unit for preserving the insulating material about wire windings of the motor, also prolongs the life of the unit. My invention furthermore improves the efficiency of the motor-compressor unit and the refrigerating system as a whole.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A refrigerating system comprising, an evaporator, a condenser, casing means forming a lubricant separating and storage chamber, a motor and'a compressor driven thereby within said chamber, said compressor having a cylinder, at superheat removing coil located outside said chamber, a refrigerant inlet for said cylinder, a discharge valve for said cylinder, means for conveying compressed refrigerant from said discharge valve out of said chamber and into said coil, a pressure relief valve for said cylinder, means preventing liquid from said pressure relief valve from entering said chamber and for directing the liquid out of said casing means in a path separate from' said compressed refrigerant conveying means and closed off from said chamber around said compressed refrigerant discharge valve directly into said coil, an outlet from said coil thereafter discharging fluid partially cooled therein into said lubricant separating and storage chamber, an outlet from said chamber through'which the compressed refrigerant is discharged into said condenser, and fluid flow connections between said condenser, said evaporator and said compressor cylinder refrigerant inlet.

2. A refrigerating system comprising, an evaporator, a condenser, a casing forming a lubricant separating and storage chamber, a motor and a rotary compressor driven thereby within said chamber, said compressor having means forming a compressionchamber including a cylinder element, end plates on opposite sides of said cylinder element and an impeller operated by said motor within said cylinder, a superheat removing conduit coil located outside said chamber, a discharge valve associated with one of said plates through which gaseous refrigerant compressed by said compressor flows, means communicating with said discharge valve for conveying the compressed refrigerant out of said casing into said coil, a pressure relief valve associated with the other of said plates, a passageway communicating with said pressure relief valve and extending through said other plate, said cylinder element and said one plate preventing liquid discharged from said pressure relief valve from entering said chamber and for conveying the liquid in a separate path closed off from said chamber around said discharge valve to said compressed refrigerant conveying means and directly into said coil, an outlet from said coil thereafter discharging fluid cooled therein into said lubricant separating and storage chamber, an outlet from said chamber through which refrigerant is discharged into said condenser, and

fluid flow connections between said condenser, said evaporator and said compressor compression chamber.

References Cited in the f le of this patent UNITED STATES PATENTS 

